Electron discharge device of the magnetron type



Sept. 28, 1948. SPENCER 2,450,023

ELECTRON'DISCHARGE DEVICE OF THE MAGNETRON TYPE Filed Nov. 15, 1943 IF/GZ/ 4 /6 V Z 796*. 2. a /6 74 l" "Ii", III

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Patented Sept. 2S, 1948 ELECTRON mscmincn'nnvloa OF THE MAGNETRON TYPE Percy L. Spencer, West Newton Mass assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application November 15, 1943, Serial No. 510,423

This invention relates to a magnetron and more particularly to one which has a plurality of posclose to but nevertheless different from the'fre- I quency of the principal mode, such a spurious mode seriously interfered with the effective and efilcient operation of the device.

An object of this invention is substantially to eliminate the undesired character of the additional or spurious modes of oscillation.

Another object is to devise a magnetron struc turein which one of the most troublesome spurious modes has its frequency shifted so far from the frequency of the principal mode as substantially to eliminate the undesired character of said spurious mode.

The foregoing and other objects of this invention will be best understood from the following I 3 Claims. (Cl. 315-39) description of an exempliflcation thereof, referr ence being had to the accompanying drawing wherein:

Fig. l is a transverse section of the magnetron embodying my invention, taken along line l-l of Fig. 2; and

Fig. 2 is a longitudinal cross-section taken along line 22 of Fig. 1.

The magnetron illustrated in the drawing comprises a combined envelope and anode structure it having a central opening therein within'which is disposed a cathode structure 2. The envelope is completed by a pair of end rings 3, which together with end caps 4 are soldered in place on the ends of the anode structure I. The anode structure is formed with a plurality of radiallydisposed anode arms 5, each pair of said arms surrounding a loop opening 6. Each circuit comprising each pair of anode arms 5 and the conducting path through the anode structure around each opening '8 contains predetermined values of capacity and inductance, and thus constitutes a tuned circuit which is adapted to oscillate at a predetermined desired frequency, All of said tuned circuits are intended to operate at exactly the same frequency so that all of said circuitsducting sleeve coated with electron-emissive oxides within which is placed a heating filament, not shown. The heating filament is provided with a pair of endiconductors Band I 0 projecting from opposite ends ofthe cathode structure. The conducting sleeve of the cathode is connected to one of said end conductors, for example end conductor 9, and is insulated from the other of said end conductors. The cathode structure is supported by a pairof lead-in conductors 8 which pass through a pair of conducting pipes 9 hermetically sealed through the upper and lower end rings 3. Said lead-in conductors are sealed through glass seals I0 carried at the outer ends of said pipes 91. l I I When a structure such as above'described is placed between suitable magnetic poles -I I, oscillations are generated which are pickedup by a coupling loop [2 inserted in one of the loop openings 6. One end of the couplin loop is connected to the end of a pipe l3 hermetically sealed through the wall of the envelope structure. The other end of said coupling loop is connected to the conductor ['4 which passes out through a glass seal IS-carried attheouter "endof the pipe 13. As is well known, an additional conducting pipe, not shown, maybe connected to the pipe [3 and form with thefconductor It a concentric transmission line for conducting oscillations generated by the tube-to ajsuitable utilization device.

The desired or 1ori-ncipa1 mode in which the above structure is intended to oscillate is a socalled transverse mode. When oscillating in the desired manner; adjacent anode arms 5 are of opposite voltage polarity and oscillating currents flow in'the anode structure in a substantially circula r path around loop opening'fi. As more fully described and" claimed in my copending applications; Serial No. 421,145, filed December 1, 1941, now Patent No. 24-11789, issued March 18, 194-7, and Serial No. 465,413. filed'Nov'ember '13; 1942, variousund'esired spurious modes may 'be eliminated by interconnecting every other anode arm by a conducting strap at one end of the anode structure and interconnecting the remainin anode arms by a conducting strap at the other end of the anode structure. Therefore I utilize such upper and lower conducting straps I 6 in the present structure. In addition to the transverse mode of oscillation described above, the magnetron also tends to oscillate in an undesired "longitudinal" mode, in which the upper and lower ends of each anode arm'tend to be of opposite voltage phase. Heretofore in magnetrons of the general configuration, as described above, the natural frequency 3 of such a longitudinal oscillating made has been rather close to the frequency of the principal mode. Under these conditions the longitudinal mode has seriously interfered with the efiectiveness and efficiency of the device. I have found that if each; anode. arm; is interrupted substantially centrally thereof by an openingl'l, the efiectiveness and efliciency of the device have been substantially increased. This, I believe-is due to the natural frequency.-0fetheeundesireda 4 scribed above as many equivalents will suggest themselves to those skilled in the art.

What is claimed is: 1. An electron discharge device comprising a cathode; and an anode structure spaced from said: cathode; said anode'structure including a pair of' arm members which, together with that portion of said anode structure lying therebe- -=tween, define a cavity resonator; each of said arm-members being centrally slotted in a plane -z' perpendicular to the axis of said cathode, and

thereby forming a single pair of capacity-coupled arm elements of equal lengths; all of said arm elements-presenting electron-receiving faces of troderconfigtu atlon."zz li'herlaminae llkare of: in-

ereasedrdiameter asucomnared withi-therlaminae |9;": thlIs :iorming 'aiplura'lity' ofv "ex ternalgheatra'diating "fins..=.i:Thecentral; lamina, which: may be; one .otthelaminaelit-is cut away at: itscentral region toaanilextenh substantially thessame as' the outer zendsf'ofitheeloop?openings 6. Inathis way the icentral rlamina zzconsists of a. :simple ring. f-All of the.:laminaer.are stacked. and soldered togather. ton formiptheccomposite. structure When this is done, it will be noted that each ,of the vaimde'za-rms i is interrupted substantially along its entire. length.

1 Irlbelievepthatnthe:beneficial-:efiectsnwhich are derived from; the-l above'adescribed structure are due torthevfollowingli Therfrequency; of: the lon- 'gitudinaL-modeshas heretofore. beenidetermined by.1the:total-length of. thewconductingr path' which hasyexisted =irom- :the-top: to the 1 bottom of-=each anode; arm; {The-oscillatingicircuits thus formed heretoiore: have ,had i-requencieswery close to that ,ofafthesprincipal 7 operating -:,mode..- By :diViding .eachi anode arm 5-, ,aszabovez'described, ithe, upper .andioweri halves. of eachvanode. arm are coupled togethenethroughi'thelcapacityawhich exists beequal'lengths to said cathode.

2., An .ielectron' discharge device comprising a cathode; and an anode structure spaced from said-cathode; said anode structure including a pair of arm members surrounding a loop section andiiorming. therewith a tuned oscillatory circuit;::eachf ofsaid .arm members being centrally slotted in aplane perpendicular to the axis of 'said .cathodexand thereby, forming a single pair of juxtaposed armelements of equal lengths the ad- .ja-centxsurfaces' ofwhich provide capacityizoouplingbetween said arm elements; .all of. said-arm elements npresenting electron-receiving faces of equal lengths to said cathode.

3;;An:electrondischarge device'comprislng a cathodeuand ananocle structurespa'ced from said cathode; said anode structure includinga-pair of arm members'surrounding a: loop section and forming therewith a tuned oscillatory circuit; saidanode'structurebeing formed of -a=plurality of substantially flat laminae each defining a cross-section of'fsaid tuned oscillatory circuit, with the central lamina cut away dividing each of saidt arm members ino a single pair ofjuxtaposed tweentherjuxtaposed;surfaces of said-upper-and l lowe lrportions Ems? capacity being directly interposedvintowthe. circuitw which constitutes the longitudinalloscillatingrcircuit; substantially alters-theefi equenoylthereof;l Itno longer is "close to thevfrequency 0t theiprincipal mode, butis -sub- JtOf course-ri-tis-to, be understood that this-inven- .tion is notrlimited torthe' particular-details as: de-

arm elements of equal lengths; all of said arm elements having electron-receiving faces of equal lengths-disposed adjacent said cathode.

PERCY L; SPENCER.

. 'REFERENCES. CHTED following references are of record in the file'o'f'this patent:

. UNITED STATES PATENTS Number Name Date 1,778,829 Harrington Oct. 21, 1930 1,978,021 Hollmann Oct. 23, 1934 2,043,733 Brasch et a1. June 9, 1936 2,063,342 Samuel Dec. 8, 1936 12,250,698 Berline July 29, 1941 -"2,408,903 Biggs et al. Oct. 8, 1946 2,422,465 Bondley .June 17, 1947 u OTHER REFERENCES Procfl. R. 13.; March 1944, pages 137, 13 8. 

